@olli_s Yes, I managed to get it working using chrome first, however this is likely to be an issue with other firefox users.

The problem does seem to be with firefox only (even with add-ons disabled).
Basically when you login on most sites for the first time, firefox asks if you wish to save login and password details to make it easier next time. Some https sites block this, but there are bookmarklets which up till now have allowed those sites to have their passwords saved also.
The website (as you mentioned) is https://carma.secteer.com/personal-carma/ https://vulndetect.com/?1
When I logged in the first time in chrome, it offered to save the login details as normal. I was then able to import passwords from chrome to firefox.
(Apologies for the stressy first post, I was already having a bad morning before this!)

OK NVM, I got it working on another browser, must be a firefox thing. First site of many that I have had this issue with though , so something must be different.

Login page at the Secteer website is broken and will not allow browsers to remember passwords (why do people do that?)
Uninstalling, will try again if this gets fixed.